Continuity mistake: When Joker and Rafterman are in transit on the chopper, we see the gunner firing out the cargo door. We can see out the cargo door that the ground is pretty far away, the chopper is obviously pretty high up in the air, so high that if there were people down on the ground it would be rather hard to see them. However the camera switches to the gunner's point of view shooting at people, and the chopper only seems to be about 20 feet off the ground.
Factual error: In the sniper scene where Animal Mother disobeys Cowboy to go help 8-Ball and Doc, and Animal Mother peeks around the corner of a building to try and see the sniper and the sniper shoots at him, narrowly missing his face, the impact of the sniper's bullet on the wall and the sound of the gunshot occur a split second before the muzzle-flash in the distant window from where the sniper is shooting from. This would imply that both bullet and sound have travelled faster than light. (01:37:15)
Revealing mistake: When Private Pyle shoots himself you can see that the blood splatters from the side of the screen instead of going straight back from the back of his head.
Continuity mistake: When Hartman punches private Joker you can see Hartman swing with his left hand in one shot and a split second later (angle from the floor) when Joker has been struck, Hartman's right hand has made contact and is pulling back.
Continuity mistake: In the part of the death of Cowboy, before he looks through the corner of the building to see the position of the sniper, there is a wall in good condition behind another wall which is broken. Later, when he goes back and starts to give orders, the wall that was in good condition is now broken without any reason for it to be and now the sniper can see Cowboy so she can shoot him. (01:39:20)
Revealing mistake: In the early latrine scene when Privates Cowboy and Joker are mopping the floor, the mops they are using are dry. As they dip each mop into the bucket, there is no water dripping. When they move the bucket, the sound indicates it is empty, as anyone who has ever used a mop & metal bucket could validate.
Revealing mistake: We find out at the end of the movie that the sniper is a young girl, but earlier when the first shot is taken at Eightball, you can see the sniper's fingers on the fore end of the rifle - they appear to be an adult male's fingers. (01:31:27)
Factual error: When Pvt. Pyle commits suicide, he shoots himself through the skull at point-blank range with the tile wall of the bathroom only inches from the back of his head. The wall becomes splattered with blood and brain tissue but no hole in the wall is visible. Both the shot through Hartmann and the one through Pyle would have punched through the bathroom walls and quite possibly caused injury or death to anyone on the other side. (00:44:09)
Continuity mistake: When Joker goes to see Cowboy and the squad are sitting in the temple, the dead Vietnamese's face can be seen without the hat covering it. When the photo is taken by Rafterman, his hat appears and is removed.
Factual error: At one point Joker is doing chin ups, with Hartman motivating him. Joker does three chin-ups, but not a single one of them was done properly. You're supposed to lock your elbows all the way out on the way down, and your chin needs to clear the plane of the bar. Joker never locks his arms out, barely gets over the bar. In reality Hartman would have been all over him about this, drill instructors are notoriously strict about proper technique.
Revealing mistake: When Joker and Raptor are in the helo heading for the front, there is a view of Vietnamese being fired at by the door gunner with an M-60 machine gun. Several seconds pass in the scene while bullets should be tearing into the ground around them, but there are no indications of bullet strikes, even as the line of fire passes over a small creek.